Targeting device for an implant

ABSTRACT

The invention discloses a two- or three-axis transmitter positioner driven by a pulsed DC current, external to the patient, coupled with three- or two-axis receivers positioned internal and/or external to the implant. The receivers are sensitive to a transmitted DC magnetic field emanating from the activated transmitter. Receiver signal processing electronics control the receiver and serve to convert its output to a format suitable for processing by a digital computer in conjunction with a method for processing received signals so as to thereby develop position and orientation data of the transverse locking holes or pin placement. Such data then can be graphically displayed to the user so as to guide the user for accurate alignment of a drill bit with the transverse holes in the implanted device.

This application is a continuation-in-part (CIP) of U.S. applicationSer. No. 09/013,827 filed Jan 27, 1998, now U.S. Pat. No. 6,074,394.

FIELD OF INVENTION

The invention relates to the positioning of a first element, relative toa second device, through the use of direct current magnetic fieldgenerating and receiving devices, and more particularly, to theinstallation of orthopaedic implants. More particularly, it relates toan improvement over existing devices used for locating holes in animplanted prosthesis so that a screw or pin for interlocking theprosthesis either with itself or with the surrounding bone can beaccurately installed. The invention specifically relates to a positioneror aiming (targeting) device for locking screw or pins for suchorthopedic hardware which employs pulsed direct current (DC) transmittedsignals to enable precise positioning of such screws or pins.

BACKGROUND OF THE INVENTION

Various intramedullary nails and targeting devices for interlocking theintramedullary nail to the surrounding bone, particularly for the use inrepairing the femur, are known in the prior art. One targeting methodthat is capable of providing precise locating of the holes distally usesx-ray techniques, but long periods of x-ray exposure are required andthe need to move the x-ray equipment in and out of position to check thescrew or pin locations means that there is a risk of a loss of alignmenteach time the equipment is moved. Patents of interest in this fieldinclude U.S. Pat. No. 5,537,453 (Williams et.al.); U.S. Pat. No.5,478,343 (Ritter); U.S. Pat. No. 5,426,687 (Goodall et al); U.S. Pat.No. 5,178,621 (Cook, et. al.); U.S. Pat. No. 5,031,203 (Trecha); U.S.Pat. No. 5,030,222 (Calandruccio et al); U.S. Pat. No. 5,013,317 (Coleet al); and others as cited in the above patents. As a consequence ofthese radiographic techniques, the positioning of such locking screws orpins is typically the most time consuming and difficult portion of theoverall rod implantation procedure.

Two other patents are thought to be of more general interest, U.S. Pat.No. 4,625,718 (Olerud et al.), and U.S. Pat. No. 4,570,624 (Wu). TheOlerud et al. patent disclosing an aiming apparatus using X-raytechniques for making holes or bores in the bone of a patient inregistration with the holes or bores on an interlocking nail, and the Wupatent disclosing a mechanical technique for aligning surgical pins inparallel.

Patents of interest in this field include U.S. Pat. No. 4,621,628(Brudermann); U.S. Pat. No. 5,049,151 (Durham et al); and U.S. Pat. No.5,514,145 (Durham et al). The Brudermann patent discloses an apparatusfor locating transverse holes in the distal end of implanted lockingnails. The apparatus includes at least one magnet which generates anaxially symmetrical field, in combination with a magnetic fielddetecting device or sensor having an axial field receptioncharacteristic. In one embodiment, the magnetic field sensor is insertedinto an implanted nail and the magnet, which is placed on the surface ofthe skin, is moved until axes of the magnetic field of the magnet andthe sensor are aligned. More particularly, the sensor is connected to anexternal display device and alignment of the respective magnetic fieldsis indicated when a zero-point indication is provided on the displaydevice. A second magnet can be used to increase the precision of thealignment process. The directional characteristics of the magnetic fielddetection device are used to control the relative positions of the axesof both directional elements through a display device, such that bothaxes are brought into congruence with each other by means of the controldisplay. When one of the directional elements is aligned exactly withthe axis of the of the transverse hole in the in the nail, anotherelement can be used externally to mark the location of the nail hole forpositioning of a drilling jig.

The two patents by Durham et al. relate to a method and apparatus forpositioning the screws or pins of orthopedic hardware devices such asintramedullary rods which involves the positioning of a first magnet atthe location of a screw hole in the nail and then using an aimingdevice, comprising a second magnet which interacts with the firstmagnet, to locate the first magnet and hence enable a screw or pin to beplaced in the screw hole in the nail to lock the nail in position.

In one first embodiment, an insertion rod is used to position the firstmagnet at the level of the hole in the rod while in another embodiment,a solid nail is used and the magnet is removable disposed within thehole in the nail prior to implantation of the nail.

One serious disadvantage common to the magnetic field detection devicesis the detrimental influence of stray magnetic fields, such as, forexample the earth magnetic field, or the effect of field distortion dueto highly conductive materials in the form of aluminum, titanium,stainless steel and copper used in the construction of operating roomtables and surgical implants. The art of using transmitting andreceiving components with electromagnetic coupling for measuringposition and orientation is well known especially with respect toarmament sighting systems where the receiver component would be locatedin gunner's helmet and a transmitter component would be attached to anearby electrically non-conductive structure. As the gunner wouldsight-in a target through a sighting cross-hair affixed to his helmet,the receiver located thereupon would pick up signals generated by thetransmitter. These signals would then be processed by a computer todetermine the position and orientation of the helmet and then tocontemporaneously point a unit of armament in the same direction as thehelmet mounted sight piece. As taught in U.S. Pat. No. 4,054,881 (Raab)and U.S. Pat. No. 4,287,809 (Egli et al.), and U.S. Pat. No. 4,314,251(Raab) and U.S. Pat. No. 4,396,885 (Constant), an alternating current(AC) signal is applied in a time division or frequency division formatto a transmitter consisting of two or three orthogonal coils whichgenerate an AC electromagnetic field which is measured by an AC receiverlikewise consisting of three or two orthogonal coils. These sensedsignals are then filtered and amplified in a method compatible with thetransmitted format, converted to a digital format and then read into acomputer where various mathematical methods are resorted to in order toextract position and orientation with resort to applicableelectromagnetic field equations.

All current systems such as the ones above, that utilize an ACtransmitted signal work accurately only when there are no electricallyconductive materials located near either the transmitter or receiverbecause any transmitted AC signal would invariably induce eddy currentsin these conductive materials which would in turn serve to generate anAC magnetic field that would distort any transmitted field, and, ofcourse, any ultimate out-put position and orientation data. In fighteraircraft or helicopters where it is desired to use these position andorientation measuring systems, there are a lot of highly conductivematerials in the form of aluminum, titanium, magnesium, stainless steel,and copper used in the construction of the cockpit structure, seat,wiring and helmet-mounted displays. U.S. Pat. No. 4,287,809 teaches amethod of compensating for the errors resulting from any fielddistortion due to cockpit metal that does not move with respect to thetransmitter. The compensation method therein suggested involves makingmeasurements throughout the cockpit to determine the amount of suchdistortion and then using this data to form a correction that is appliedto the sensed signals. In a similar manner, U.S. Pat. No. 4,394,831(Egli et al.) and U.S. Pat. No. 4,621,628 (Brudermann) teaches a methodto accomplish compensation for errors due to eddy currents induced inmetal such as would be found in a display located on a pilot's helmet oroperating field, respectively. This compensation method again requiresinitial experimental measurements of such distortion in order to effectnecessary corrections and provides moderate improvements in accuracyonly when the amount of metal is concentrated in a single location andthe transmitter does not go through large angular rotations ortranslations. These types of compensation efforts that are required tomake AC systems work accurately are time consuming and expensive toperform and only work in environments where there would not be too muchconductive material near transmitter or receiver units. In manylocations, for example, AC systems cannot be utilized at all because thedistortions produced are simply too large to be corrected merely by suchmapping.

It is the object of this invention to provide an effective andeconomical device for the determination of the location and orientationof the holes in orthopaedic implants. Still another object of thepresent invention is to provide a targeting device which can be utilizedby the majority of current intramedullary nails currently available tothe surgeon.

SUMMARY OF THE INVENTION

The invention includes a two- or three-axis transmitter positionerdriven by a pulsed DC current, external to the patient, coupled withthree- or two-axis receivers positioned internal and/or external to theimplant. The receivers are sensitive to a transmitted DC magnetic fieldemanating from the activated transmitter. Receiver signal processingelectronics control the receiver and serve to convert its output to aformat suitable for processing by a digital computer in conjunction witha method for processing received signals so as to thereby developposition and orientation data of the transverse locking holes or pinplacement. Such data then can be graphically displayed to the user so asto guide the user for accurate alignment of a drill bit with thetransverse holes in the implanted device.

The devices presented in U.S. Pat. Nos. 4,945,305 and 4,849,692 (Blood)represents a radical departure from all of the prior art relating tosuch transmitting and receiving position and orientation devices,insomuch as it avoids, in-toto, resort to AC signals and instead reliesupon direct current (DC) signals. Such reliance on DC signals obviatescompletely any need for a prior calibration undertakings and greatlyexpands the potential utility of devices of this type. Moreover,manufacture and utilization of this device for purposes of accomplishingall that current devices can accomplish is manifestly less expensivethan such manufacture and utilization of said currently used devices areor potentially will be.

It has now been found that the use of the devices of U.S. Pat. Nos.4,945,305 and 4,849,692, the disclosure of which are incorporated byreference herein, as though recited infull, can be applied to theinstallation of orthopaedic implants and, more particularly, to thelocating of holes in an implanted prosthesis so that a screw or pin forinterlocking the prosthesis either with itself or with the surroundingbone can be accurately installed, with surprising effective results.

The invention provides a system of transmitting and receiving antennaethat by themselves intrinsically and with inherent electronic meanstogether with a digital computer readily measure position andorientation relative to one another without the need for expensivecalibration procedures undertaken in advance of implementation andfurther without concern for what types of diamagnetic or paramagneticmetallic materials such as may be nearby. For the first time, forinstance, devices of this nature can be used in surgical procedures inconjunction with metallic implants and surgical apparatus.

The invention provides for the determination of the displacement vectorand determination of the orientation of the orthogonal axis of thereceiver relative to the transmitter, FIG. 1. The transmitter isconsidered the origin of an orthogonal coordinate system of x, y, and zcoordinates wherein the z-axis is considered, generally, in line withthe gravitational axis of the earth, the x and y axes then lie in thehorizontal plane, perpendicular to the z axis and according to aCartesian coordinate system. The Cartesian system consists of threemutually perpendicular lines or axes that intersect at a common pointsuch that the location of a point relative to the origin can bedetermined without ambiguity. In addition, each receiver establishes areference coordinate system with respect to the respective receiver andrelative to the transmitter origin such that the location of thereceiver can be determined from the transmitter, as well as the rotationof each axis of the receiver system relative to the transmitter. It isan advantage of the invention that the coordinate reference system ofthe receiver can be electronically offset to a desired location usingthe inherent electronic means together with a digital computer. As shownin FIG. 6, the reference axis S1 of receiver 107 at location r1 can beelectronically offset to a location r1′ with a reference axis S1′ suchthat the location vector and the angular orientation of the axis S1′from the transmitter can be ascertained. Likewise, the receiver axis ofeach receiver can be offset to any desired positioned.

It is a further advantage of the invention that the relative positionand orientation between two or more offset locations can be ascertainedusing the inherent electronic means together with a digital computer. Itis a further advantage that the relative distance between two or moreoffset axes can be minimized such that one or more of the relativecomponents of the relative displacement vector be minimized and thecorresponding axes aligned in space.

The invention provides a distinctly less expensive sighting device thanis currently provided within the framework of the present state of theart separate and apart from the cost savings to be realized fromabrogation of calibration requirements. Presently, the cores of thetransmitting components of these devices are made up of Ferrite. Ferriteis rather expensive, but, in addition to this, it is also rather fragileand difficult to shape. However, Ferrite is necessary as a core piece inorder to keep eddy current distortion acceptably low where AC current isused. But, there are no AC signal components in the instant device'ssteady state signal and hence, the same magnetic flux concentration ascan be had with Ferrite can likewise be had and used with this device byresorting to less expensive iron or steel for a transmitting core piece,since, with this device, there is no need to be concerned with eddycurrents at all.

The instant invention provides a targeting apparatus which does notrequire the use of radiographic radiation in determining the location ofthe transverse holes of intramedullary implants, particularly of thedistal holes of interlocking nail. The apparatus of the presentinvention provides, fast, convenient and secure placement of thedrilling jig in axial alignment with the transverse holes withoutinvolving the radiation exposure on the surgeon, patient, and othermedical personnel. The current surgical practice in the use of the imageintensifier to locate the unseen transverse holes in the implant and totarget the hole for drilling and placement of interlocking screwsexposes the surgeon to excessive amounts of radiation during the courseof the procedure.

Another advantage of the present invention is that it provides atargeting device which can be utilized by the majority of currentintramedullary nails currently available to the surgeon. The currentmechanical locating devices are usually implant specific and require theuse of the image intensifier to locate the orientation of the distallocking holes. The Distal Targeting Device described in theRussell-Taylor Surgical Technique brochure (Smith & Nephew Richards,Memphis Tenn.) is a “bombsite” apparatus which is mechanically fastenedto the proximal end of the nail and utilizes the image intensifier tolocate and drill the necessary holes. The mechanical targeting systemdescribed in U.S. Pat. No. 4,913,137 is specific to that device. Thetargeting mechanism described by Azer et al requires that the describednail have a bifurcated tip, a cross section complimentary to otherinstrumentation, and a mechanism for attachment to the proximal end ofthe nail. The rod mounted targeting mechanism described in the surgicaltechnique for the Alta Trauma System by Howmedica (Rutherford, N.J.)requires the initial location of the distal holes, the attachment of thetargeting assembly mechanism to the nail, and further fluoroscopiccontrol to position the targeting assembly over the distal holes.Another technique used for the above systems, as well as all the othernail systems, requires the use of direct fluoroscopic imaging to locateand align the holes with out any mechanical or electrical connections iscalled “free handing”. This technique is described in detail in thebrochures by Smith & Nephew Richards, Zimmer (Warsaw, Ind.), Ace Medical(Los Angeles, Calif.) and Biomet (Warsaw, Ind.).

The described technique and devices of the present invention can becustomized for any of the described intramedullary nails.

In accordance with the invention, a DC coupled electromagnetic sensor isprovided which is easier to use than prior art devices and whichprovides easier and more accurate alignment than is afforded by theprior art. In this regard, although the positioner arrangement of theBrudermann and Durham et al. patents discussed above possesses a numberof important advantages over the radiographic locator devices, thepresent invention provides important additional advantages over thepositioner arrangement disclosed in those patents, particularly in theareas of ease of use and ease and quality of the alignment.

In one aspect of the invention, a DC coupled electromagnetic positioningsystem is provided for assisting in positioning a fastening element at adesired concealed internal location such as at a locking screw hole inan intramedullary rod in the bone of a patient, the arrangementcomprising: a pulsed DC current transmitter, a first receiver, or aplurality of receivers, that is sensitive to the transmitted DC magneticfield adapted to be positioned at said internal location and providing atwo or three axis directional reference or coupled with the implant at aknown offset location and orientation from the internal location to bepositioned; and a second or additional receivers thus providing multiplereference positioning devices external to the patient; the positioningdevice comprising a hand-held drilling jig or guide drill having anaxial bore there through, so as to enable the external receiver to alignwith the internal or couple receiver, the positioning device furthercomprising a guide pin insertable into the axial bore and adapted to beengaged by the drill chuck of said drill when the perceived axes of thefirst and second receivers are aligned so as to enable the guide pin tobe advanced by the drill along a path of travel in alignment with theinternal location.

In an advantageous embodiment, the said first receiver or internalsensor unit is embedded in a unit or handle to which the implanteddevice is attached. The location and orientation of the receiverrelative to each internal concealed location to be positioned can beknown through either physical measurement or electronic determinationusing a calibration routine. In an advantageous embodiment, the saidfirst receiver or internal unit includes a protective cover. Preferably,the protective cover comprises a plastic casing advantageously shaped tomatch or conform to the internal shape of the particular intramedullarydevice being implanted. Thus the embodiment of the invention involvesthe provision of a locating arrangement that can be used with anycommercial nail.

In an advantageous embodiment, the perceived position of the first andsecond receiver, or additional receivers, relative to the transmitter,can be electronically offset by the connected computer so as to providea perceived location and axis in space, relative to the sensors. Theadvantage of this embodiment is that the position and axis of thetransverse holes can be ascertained without the sensor being physicallyat the location. With both the first and second sensors offset to thesame position, an axis and location of the transverse hole can belocated and a drill or pin passed through the hole without interferencefrom the sensor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates the components of the invention and positioning of aninterlocking nail 120 in the medullary canal of a bone 110.

FIG. 2 illustrates the coordinate axis for the transmitter 104 andreceiver 107.

FIG. 3 illustrates the intramedullary nail

FIG. 4 illustrates the nail driver and associated components

FIG. 5 illustrates the drill guide and drill sleeves

FIG. 5A illustrates the drill guide and drill sleeves

FIG. 5B is an exploded view of the drill sleeves for use with the drillguide of FIG. 5A

FIG. 6 illustrates the displacement vectors of the receiver 107 andreceiver 109 and axis offset positions to the transverse hole 121 andaxis of drill guide bole 132, respectively, relative to transmittercoordinate origin 201.

FIG. 7 illustrates the calibration tool used with the grill guide andintramedullary nail.

FIG. 8a illustrates the application of the invention with the receiverpositioned within a probe inserted in the intramedullary nail.

FIG. 8b illustrates the cross section of different shaped probe headscomplimentary to the intended implant 120.

FIG. 9A is a perspective view that illustrates the components of theprobe when used with a circular cross section implant.

FIG. 9B is a side view of the probe of FIG. 9A.

FIG. 10 is a perspective view of the disclosed system being used tosecure a bone plate.

FIG. 11 is a perspective view of a bone plate

DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

A first component, such as an orthopaedic implant, and more particularlyan intramedullary nail is provided with at least one connector receivingmechanism. In the case of an intramedullary nail, the connector can be ascrew and the connector receiving mechanism can be holes in the nail. Adrill guide member, is used to guide a drill bit towards a selected holein the nail. The drill bit is positioned and oriented by the drill guidemember relative to the intramedullar nail. The guiding system includes:

(a) a direct current magnetic field transmitting member;

(b) at least one magnetic field receiving means for receiving thetransmitted direct current magnetic fields;

(c) power means for supplying direct current electrical signals to thetransmitting means for creating the transmitted direct current magneticfields;

(d) receiver electronics for measuring, and converting out-put signalsfrom the magnetic field receiver electronics, into position andorientation measurements; and

(e) programmed computer, the programmed computer having a visual displaymember, the output signals from the receiver electronics being convertedinto position and orientation measurements and visually displayed on thecomputer visual display member.

The first component is fixed to either the transmitting member or thereceiving means. Similarly, the drill guide member is fixed to either atransmitting member or a receiving means.

Preferably, the system employees a single transmitter, and both thedrill bit guide member and the intramedullary nail are provided withreceivers. Thus, the relative position and orientation of the firstmember relative to the drill guide member can be determined. Theintramedullary nail has a proximal end and a distal end. A supportmember, such as a handle, is releasably secured to the proximal end ofthe nail and carries a receiver. The transmitter for transmitting directcurrent magnetic fields comprises a core and a multiplicity of roughlyorthogonal antenna axis wire windings. The receiver of the transmitteddirect current magnetic fields comprises a multiplicity of roughlyorthogonal antennae axes that are sensitive to transmitted directcurrent magnetic fields.

The method of securing an implant, such as an intramedullary nail into abone includes the steps of inserting the implant into a bone, drilling ahole in the bone proximate the screw receiving hole in the nail, byusing a drill member and a drill guide. The determination of theposition and orientation of the drill member relative to the holesinvolves (a) transmitting a direct current magnetic field from atransmitting member, receiving the transmitted direct current magneticfields at at least one magnetic field receiver. The nail is fixed toeither the transmitting member or the receiving means, preferably, thereceiver. Similarly the drill guide is fixed to either a transmittingmember or the receiving means, preferably, the receiver. The receiveddirect current magnetic fields are converted into position andorientation data in a programmed computer, and displayed on the computerscreen. By viewing a virtual representation of the nail and the drillmember on the computer screen, the drill member can be moved to thedesired location relative to the intramedullary nail.

Advantageously, the nail receiver can be remote from the screw receivinghole so that the receiver need not be carried into the bone along withthe nail. The computer program calculates the offset from the receiverto the hole, and thus, the display shows the position of the holerelative to the drill.

In FIG. 1, the nail 120 has been driven into the bone 100 from the rightside, and the nail has in the vicinity of its left, i.e. distal end 125a pair of transverse holes 121 and 121 and in the vicinity of its right,i.e. proximal, end a transverse or oblique hole 121″ for receivingtransverse bolts 326, 326, and 326″, FIG. 3, respectively.

Next, the exact position of the respective drilling axis 321 of a mostdistal hole 121 in the intramedullary nail 120 is to be determined. Thisdrilling axis can be definitely determined by a linear connecting lineof the two center points 322 and 323 on this axis. In order to place adrilling jig 131 in a position aligned with this axis, the two points322 and 323 on the drilling axis of the distal hole 121 must be locatedaccordingly, and the axis of the drilling jig 532 must be oriented inaccordance with these points, whereupon the hole (bore) may be formed inthe bone immediately.

The apparatus according to the invention is used for locating the axis321 generated by these two center points 322 and 323. Theelectromagnetic position and orientation measuring system, as describedin U.S. Pat. Nos. 4,945,305 and 4,849,692, consisting of: a transmitterdriver circuit within an electronic control unit 102 for providing acontrolled amount of DC current to each of two or three axes oftransmitter 104 one at a time. The amount of DC current provided bydriver 102 to the transmitter to the signal processing electronics, viaconnection 106, is controlled by the computer 101. The transmitter 104is usually located within a few feet of distance from a patient's leg.

In FIG. 2, transmitter 104 consists of three individual antennae 105 (x202, y 203, and z 204 axis, FIG. 2) arranged concentrically whichgenerate a multiplicity of DC magnetic fields that are picked up byreceiver 107 and receiver 109, (FIG. 1) of the receivers 107 and 109 arealso each composed of three antennae (x 212, y 213, and z 214 axisantennae). Receivers 107 and 109 measure not only the fields generatedby transmitter 104 but also the earth's magnetic field to thereby effectan ultimate measurement of the position and orientation of the object towhich it is attached. The transmitter antennae represent a Cartesiancoordinate system 105 with an origin 201 located at the center oftransmitter 104 and having three orthogonal axes; an X axis 202, a Yaxis 203 and a Z axis 204. Likewise, each receiver 107 and 109 havereceiving antennae which represent a Cartesian coordinate system 210 and220, respectively. The coordinate system 210 of receiver 107 has anorigin 211 located at the center of receiver 107 and having threeorthogonal axes; an X axis 212, a Y axis 213, and a Z axis 214. Notshown in FIG. 2, but numbered accordingly, the coordinate system 220 ofreceiver 109 has an origin 220 located at the center of receiver 109 andhaving three orthogonal axes; an X axis 222, a Y axis 223, and a Z axis224.

Receiver 107 and 109 consists of three or two axes, 210, 220,respectively, with driving and detecting circuits that are sensitive toDC magnetic fields. The DC signal output from receiver 107 goes to thesignal processing electronics 102 via connection 108. Signal processingelectronics 102 controls, conditions, and converts analog receiversignals into a digital format that can be read by computer 101. Computer101, by way of an algorithm, computes the position and orientation ofreceiver 107 and 109 with respect to transmitter 104. Computer 101 thenoutputs this information to a graphic image controller by which thesurgeon can view the relative position of the guide 131 with respect tothe nail driver 140 and thus to the axis 321 of hole 121 of FIG. 3A.

As illustrated in FIG. 4, the receiver 107 is mounted on, or is embeddedin, a driver unit 140 used to implant the nail 120 in the bone 100. Thenail driver 140 is comprised of a handle 401 and longitudinal body 402.The longitudinal body 402 has a longitudinal cylindrical bore 404 withcentral axis 403 which is coincident with the longitudinal axis of theintramedullary nail when attached securely to the nail using thespecific nail attachment 141 and connecting bolt 142 and locking nut143.

Nail attachment 141 has an indentation or similar means to align withthe protrusion 406 and 406′ or other mechanism on end 405 of thelongitudinal body 402. Nail attachment 141 has a central bore 415extending the longitudinal axis of the attachment coincident with thecentral axis 403. The nail attachment has protrusions 411, on the endopposite from the end having indentations 413, 413′ to provide alignmentof the attachment with the indentations 325 located on the proximal end124 of intramedullary nail 120 as shown in FIG. 3A.

A connecting bolt 142 comprised of threaded end 410, body 423, andthreaded end 421 is used to fasten and align the nail 120 with the naildriver 140. Bolt end 410 is formed to mate with the threads 324 on theproximal end 124 of the nail 120. The attachment spacer 141 is slid overthe bolt 142 by placing the bolt 142 through the central bore 415. Thenail driver 140 is likewise slid over the bolt by placing the boltthrough the cylindrical bore 404 of nail driver body 402 such that theprotrusions 406 and 406′ interlock with indentations 413 and 413′,respectively. With the spacer 141 engaged with the nail 120 and naildriver 140 engaged with the spacer 141, the locking nut 143 is threadedon threads 421 of the connecting bolt 142.

Receiver 109 is preferably attached to, or embedded in a hand-held guide131 of FIGS. 5A and 5B. Guide 131 is constructed to receive an outersleeve 134 within the drill guide hole 132. Inner sleeve bore 525 has anentrance 132 and a central axis 532. Drill sleeve 133, has a centralbore 533 enabling drill bit 135 to be coincident with the longitudinalaxis 532 when drill sleeve 134 is inserted in bore 525.

The controlling computer 101, by way of an algorithm, is able toelectronically transpose, both in translation and rotation, the axis 220and x 222, y 223 and z 224 to a new location 520 such that the offsetcoordinate axis can be located on the longitudinal axis 532 or thecentral bore 533. The computer then computes the position andorientation of the offset axis 520 with respect to transmitter 104.Computer 101 then outputs this information to a graphic image controllerby which the surgeon can view the relative position of the drill guideaxis 532, as viewed as cross-hairs 112 in FIG. 1, with respect to thenail driver 140, as viewed as cross haris 111, in FIG. 1, and thus tothe axis 321 of hole 121.

Likewise the computer 101 by way of an algorithm, is able toelectronically transpose, both in translation and rotation, the naildriver's receiver axis 210 to a new location 310 such that the offsetcoordinate axis can be located on the axis 321 of hole 121. The computerthen computes the position and orientation of the offset axis 310 withrespect to transmitter 104. Computer 101 then outputs this informationto a graphic image controller by which the surgeon can view the relativeposition of the drill guide axis 532 (cross haris 112) with respect tothis offset axis 310 and thus to the axis 321 of hole 121 (cross hairs111).

The mathematical relationship for the distance from the offset axis ofthe transverse hole 310 to the offset axis 520 of the drill guide 131can be derived from the position vectors (small letters in bold). FIG. 6presents a schematic of the position vectors of the system. T is thelocation of transmitter axis 104 (0,0,0) from which the positions, r1 tothe axis S1 210 (x1, y1, z1) of the sensor 107 embedded in the nailholder 140, and r2 to the axis, S2 220, of the sensor 109 embedded inthe drill guide 131 are measured electronically by the computer 101 andelectronic control unit 102. Likewise the orientation of the offsetaxes, S1′ 310 and S2′ 520, are determined relative to the sensor axes,S1 210 and S2 220. The transverse hole to be drilled has an axis S1′ 310which is physically positioned, r1′−r1 from S1 210. This offset positionvector, r1′−r1, is determined at the time of surgery, prior toimplantation, as part of the calibration procedure. This value will bedependent upon the length of the nail chosen as well as the orientationof the transverse hole. The drill guide hole in the drill guide has anaxis S2′ 520 which is offset from sensor axis S2 220 by a distancer2′−r2. The offset position vector, r2′−r2 is a constant which isdetermined from the manufacturing of the drill guide unit 131 and storedin the software. Therefore knowing the above vectors, the vector,r2′−r1′ can be determined from the vector relationships:

(r 2′−r 1′)=r 2−r 1+(r 2′−r 2)−(r 1′−r 1)

The software algorithm stored in the computer 101 will provide therelative distance and orientation of the offset holder axis to thenail's transverse hole which in turn can be viewed on the computermonitor by the user.

Procedure for Using the Device

The distance and orientation, as depicted by the vector (r2′−r2, FIG. 6)of the axis of the drill guide hole 532 relative to the drill guidesensor 109 are constant and known. However, the distance from thereceiver 107 in the driver to the axis 321 of the intended hole 121 willbe dependent upon the length of the intended implant 120 as chosen bethe surgeon. Thus prior to insertion, the distance and orientation ofthe transverse hole(s) 121 relative to the holder receiver 107 must bedetermined. This can be performed in a simple “calibration” procedure.

The computer 101 determines the position of the receiver 107 relative tothe transmitter 104, but it is desirable to know the position of theaxis 321 of the transverse hole 121 relative to the holder sensor. A“calibration” must be performed to determine the offset distance, vectorr1′−r1, from the holder receiver 107 to the axis 321 of the transversehole 121. An alignment pin 700, as illustrated in FIG. 7, is composed ofan initial cylindrical segment 705 which is of such diameter orcomplimentary shape as to fit into bore 525 or bores 533 or 543 of thedrill sleeve 133 or 134, respectively, a central section 710, and athird section 715 which is of such diameter or complimentary shape as tofit into holes 121 and 122, is placed in the drill guide hole 525 andinserted in the first of the nail's transverse holes 121. Thus thealignment pin 700 longitudinal axis 721 causes the axis of 521 to becoincident with axis 321. Thus the location of the distal hole axis 520,S1′ is now known relative to the drill guide receiver axis 210, S2, andthus to the transmitter 104 and the nail driver receive 107, S1. Withthe alignment pin 701 in place, the location and axis of the transversehole 321 relative to the nail driver receiver 107 is computed using analgorithm and digitally stored by the computer 101. The alignment pin700 and drill guide is moved to the second transverse hole 121′ and it'slocation and axis 321′ relative to the nail driver 140 is likewisecomputed and stored in the computer 101. The procedure is repeated forany additional locking holes in the nail such that the computer hasstored the location and axis of each transverse locking hole relative tothe handle sensor. Thus the relative distance and orientation of eachtransverse hole, relative to the sensor in the nail driver is known andthe computer has digitally stored the offset coordinates of each hole inthe nail for finding the hole after the nail has been implanted.

After the hole locations are stored in the computer 101, the nail 120 isinserted into the bone 100. The computer program then prompts thesurgeon to place the drill guide 131 at the first hole location 121. Astationary three dimensional cross-hair 111, representing the positionof the axis 321 of the desired transverse hole 121 is displayed on thecomputer monitor. A second three dimensional cross hair 112 is displayedon the monitor which represents the location and orientation of thedrill guide axis 321 relative to the offset axis 310 of the desiredtransverse hole 121. The surgeon then moves the drill jig until theguide's cross hairs 112 are aligned with the stationary cross hairs 111on the monitor. The axis of the drill guide 532 is now aligned with theaxis 321 of the transverse hole of the nail. The drill guide is heldfirmly in this orientation or gently taped to set it in the bone 100, adrill 134 is inserted in the drill sleeve 133 and drilled through thenail hole 121. The drill 134 is removed and a screw 326 inserted to lockthe nail with the bone. The computer is then programmed to proceed tothe second hole 121′ and the procedure repeated. The procedure isrepeated until all the holes have been locked.

In a further embodiment of the invention, as illustrated in FIG. 8,receiver 107 is be embedded within a probe head 805, connected to probe810. The electrical connection for receiver 107 would be containedwithin probe 810 and connect to the signal processing unit 102 via wire108. Correspondingly differently shaped probe heads 805 are required fordifferent nail diameters or different profile (cross-sectional) shapesof the nail, FIG. 8b, respectively, to ensure that during insertion ofthe probe head 805 that the probe head 805 does not rotate relative tothe nail 120 such that the orthogonal axes 210 of the receiver 107remains along the orthogonal axes of the nail 120.

The exact orientation of the receiver 107 at the distal end of the probehead 805 in the longitudinal direction of the nail 120 relative to theaxis of the transverse hole 321 is obtained by the fact that the spacingof the transverse hole 121 from the proximal end 124 of the nail 120,with a realistically pronounced deformation and in consideration of theelastic deformability of the probe 810 in the shank thereof, ismaintained with a sufficient degree of accuracy. For varying lengths ofnails or for the various distal holes 121 or 121′ of the nail 120, astop member 812 needs be positioned and fixed on the probe shank 810 incorrespondingly different positions prior to inserting the probe head805 into the nail 120. The probe shank 810 would have gradation markingscorresponding to the distance from the proximal end of nail 120 to thehole axis 121 minus a specified setback distance to place the probe head805 and receiver 107 proximal to the hole 121 to ensure that the probehead 805 is not compromised during the drilling procedure.

The DC signal output from receiver 107 goes to the signal processingelectronics 102 via wire 108 which controls, conditions, and convertsanalog receiver signals into a digital format that can be read bycomputer 101. Computer 101, by way of an algorithm, computes theposition and orientation of receiver 107 with respect to transmitter104, the position and orientation of receiver 109.

The position of the drill guide 131 relative to the transmitter 104 islikewise computed using the DC signal output from receiver 109 viaconnection 110 the signal processing electronics 104 and displayed onthe computer's 101 display device. The distance and orientation of theaxis of the guide receiver 109 relative to the axis 532 of the hole inthe drill guide 131 will be equal to predetermined set back distance ofthe origin of the axis 210 of the probe head receiver 107 from the holeaxis 121 or 121′. Therefore relative position of the axis of the drillguide 532 with respect to the axis of the nail hole 121 can bevisualized and aligned with the axis 321. Upon alignment of the axes, adrill is passed through the bone 100 and nail hole 121 and withdrawn. Ascrew or locking bolt 326 is inserted in through the drilled hole andnail.

After performing the above operations at the most distal hole 121, asecond bolt 326′ is placed into the corresponding hole (bore) 121′ usingthe same procedure.

After performing the above operations at the distal end, the proximalbolt 326″ is to be placed into the corresponding hole (bore) 121″, andthis operation need not be described in greater detail here since, owingto the small distance to the proximal end of the spike, a conventionallocation and drilling device as described in the referenced patents maybe used with a sufficient degree of precision for the locating of theproximal holes.

It should be noted further that the apparatus is capable of operatingeffectively even if the probe head cannot be guided by the inner profileof the implant, such as, for example, in the case of nails having acircular cross-section. In such instance, auxiliary measures may betaken in order to align or orient the probe head relative to thetransverse hole. For example, this may be effected with the aid of aholding device adapted to engage into the hole. FIGS. 9A and 9B show amethod by which the probe head 805 has finger extensions 905 and 905′with prongs 910 and 910′, respectively, and such prongs are able toengage the near edge of holes 121 and 122, respectively, thus provide arotational and longitudinal position of the probe relative to the hole.The length of the probe extension in addition to the radius of the holecan be made equal to the distance from the axis of receiver 109 and theaxis 521 of the drill guide bore 535.

In another embodiment of the invention the system is used as a targetingmeans for insertion of screws through other internal fixation devicessuch as a bone plate or sliding hip screw into bone structures. Boneplates are attached to the external surface of the fractured bone toprovide support and alignment during the healing process. As illustratedin FIG. 10, an attachment handle 1050 is temporarily fixed rigidly tothe bone plate 1000, illustrated in FIG. 11. The receiver 107 isembedded within the handle 1050 and an additional receiver 109 isembedded or rigidly attached to a drill guide 131 as referenced in FIG.1. The insertion of the bone screws to fix the bone plate 1000 would bein a manner similar to that described for the intramedullary nail. Thelocation of each hole 1121 is registered in the computer for theparticular plate 1000 being inserted or the hole location is determinedusing a calibration procedure.

After the bone plate 1000 has been positioned on the bone 100 eitherthrough an incision exposing the fractured bone or after inserting theplate 1000 through a small incision, the computer program prompts thesurgeon to place the drill guide 131 at the specific hole location 1021.A stationary three dimensional cross-hair 111, representing the positionof the axis 1321 of the desired transverse hole 1121 is displayed on thecomputer monitor. A second three-dimensional cross hair 112 is displayedon the monitor which represents the location and orientation of thedrill guide axis relative to the axis of the desired transverse hole1121. The surgeon then moves the drill jig until the guide's cross hairs112 are aligned with the stationary cross hairs 111 on the monitor. Theaxis of the drill guide 532 is now aligned with the axis 1321 of thetransverse hole of the plate. The drill guide is held firmly in thisorientation or gently taped to set it in the bone 100, a drill 134 isinserted in the drill sleeve 133 and drilled through the nail hole 121.The drill 134 is removed and a screw 326 inserted to lock the plate 1000with the bone 100. The computer is then programmed to proceed to thesecond hole 1121′ and the procedure repeated. The procedure is repeateduntil all the holes have been drilled and screws inserted.

List of Components of the Invention

100 bone

101 Computer including monitor, cpu, keyboard, other devices

102 Electronic control unit and driver circuit

103 Wires connecting 101 with 102

104 Three axis transmitter

105 Coordinate axis of transmitter 104

106 Wires connecting 102 with 105

107 Receiver sensor in nail driver 125

108 Wires connecting 102 with 107

109 Receiver sensor in drill guide 131

110 Wires connecting 102 with 109

111 Stationary crosshairs representing nail hole axis 310

112 Crosshairs representing drill guide axis 520

120 Intramedullary nail

121 Locking hole in 120

122 Locking hole connected to hole 121 along axis 321 in 120

124 Proximal end of nail 120

125 Distal end of nail 120

130 Handle of drill guide

131 Drill guide with embedded receiver sensor 109

132 Drill guide hole

133 Inner drill sleeve

134 Outer drill sleeve

135 Drillbit

140 Nail driver

141 Attachment spacer

142 Interlocking shaft

143 Locking nut

201 Origin of transmitter coordinate axis 105

202 X-axis of coordinate axis 105

203 Y-axis of coordinate axis 105

204 Z-axis of coordinate axis 105

210 Receiver 107 coordinate axis

211 Origin of receiver coordinate axis 210

212 X-axis of coordinate axis 210

213 Y-axis of coordinate axis 210

214 Z-axis of coordinate axis 210

220 Receiver 109 coordinate axis

221 Origin of receiver coordinate axis 220

222 X-axis of coordinate axis 220

223 Y-axis of coordinate axis 220

224 Z-axis of coordinate axis 220

310 Offset coordinate axis of axis 210

321 axis of hole 121

322 Axis of hole 122

323 Axis of hole 123

324 Means of attachment (threads) at end 124

325 Alignment indentation on end 124

401 Handle of nail driver 140

402 Body of nail driver 140 along the longitudinal axis of nail 120

403 Longitudinal axis of nail driver segment 402

404 Cylindrical bore along axis 403

405 End of segment 402 for attachment with 141

406 Alignment protrusion on end 405 for alignment with attachment spacer141

409 Cavity for wire 108

410 End of 141 for attachment with proximal end 124 of nail 120

411 Protrusion on end 410 for mating with indentation 325 on proximalnail end 124

412 End of 141 for attachment with nail driver end 405

413 Indentation on end 412 for mating with protrusion 406

414 Threaded internal bore of locking nut 143

415 Longitudinal bore through spacer 141

421 Threaded end of 142 for attachment with 324

422 Threaded end of 142 for attachment with 143

423 Connecting member of 142 connecting end 411 with end 412

520 Coordinate axis of center of drill hole 132 and coincident with axis521

521 Longitudinal axis of drill hole 132

525 Bore within drill guide 131 for drill sleeve 133

531 End section of drill sleeve 133

532 Longitudinal section of drill sleeve 133

533 Internal bore of drill sleeve 133

541 End section of drill sleeve 134

542 Longitudinal section of drill sleeve 134

543 Internal bore of drill sleeve 134

700 Alignment tool

705 end of alignment tool intended to coincide with drill guide bore 533or drill sleeve bore

710 central section of alignment tool 700

715 end of alignment tool 700 intended to coincide with nail hole121-122 along axis 321

721 longitudinal axis of alignment tool 700

805 Probe head with embedded receiver 107

810 Probe shank attached to probe head and containing wire 108

812 Stop member

813 Central bore of stop member 812

814 Stop member locking screw

905 Probe extension

910 Probe extension prong

What is claimed is:
 1. An apparatus for use in securing a first memberto a second member, wherein said second member is hidden from visualobservation within a third member comprising: A. a first member, saidfirst member having a first receiver and at least one connectorreceiving means for receiving a connector, B. a guide member, said guidemember having one of a second receiver or a transmitter and carryingsaid connector; C. electronics for positioning and orienting said guidemember relative to said first member connector receiving means, saiddevice having; (a) a direct current magnetic field transmitter; (b) atleast one magnetic field receiver for receiving said transmitted directcurrent magnetic fields; (c) power means for supplying direct currentelectrical signals to said magnetic field transmitter to create saidtransmitted direct current magnetic fields; (d) receiver electronics formeasuring, and converting out-put signals from said magnetic fieldreceiver into position and orientation measurements, (e) programmedcomputer, said programmed computer having a visual display member, saidoutput signals from said receiver electronics being converted intoposition and orientation measurements and visually displayed on saidcomputer visual display member, whereby the relative position andorientation of said first member connector receiving means relative tosaid guide member is determined.
 2. The device of claim 1, where saiddevice consists of a single transmitter and a plurality of receivers. 3.The device of claim 1, wherein said first member is an implant for bonestabilization, and said third member is a bone.
 4. The device of claim1, wherein said receiver electronics are provided by said programmedcomputer.
 5. The device of claim 4, said implant having a near end and afar end, and further comprising a support member, said support memberbeing releasably secured to said near end of said implant, one of saidreceiving means being fixed to said implant by being secured to saidsupport member, said connector receiving means being positionedproximate the far end of said implant.
 6. The device of claim 1, wherein said transmitter for transmitting direct current magnetic fieldscomprises a core and a multiplicity of roughly orthogonal antenna axiswire windings.
 7. The device of claim 1 wherein said receiving means forreceiving said transmitted direct current magnetic fields comprises amultiplicity of roughly orthogonal antennae axes that are sensitive totransmitted direct current magnetic fields.
 8. The device of claim 1wherein said transmitter for transmitting direct current magnetic fieldscomprises a core and a multiplicity of roughly orthogonal antenna axiswire windings, and said receiving means for receiving said transmitteddirect current magnetic fields comprises a multiplicity of roughlyorthogonal antennae axes that are sensitive to transmitted directcurrent magnetic fields.
 9. The method of calibrating and determiningthe fixed offset distance and orientation between at least two positionsrelative to third position, where the first position is the location ofa magnetic field transmitter, comprising the steps of: 1—transmitting apredetermined magnetic field from said first position, 2—positioning amovable guide element to a first of said at least two positions, saidmovable guide element having means for receiving said predeterminedmagnetic field, 3—receiving said predetermined magnetic field at saidfirst of said at least two positions, 4—receiving said predeterminedmagnetic field at a second of said at least two positions, 5—computingthe fixed distance and orientation offset between said first positionand said second position of said at least two positions, 6—storing in acomputer data memory, the computed data representing said fixed distanceand orientation offset between said first position and said secondposition of said at least two positions, whereby said movable guidemember at said second of said at least two positions can be reproducablylocated relative to said first of said at least two positions, by meansof magnetic fields transmitted from said first position.
 10. The methodof claim 9, further comprising the steps of determining the fixed offsetdistance and orientation of a plurality of offset positions relative toa single predetermined position, by repeating steps 1 to 6, for each ofsaid plurality of offset positions.
 11. The method of claim 9, furthercomprising a mounting member, a receiving means fixed to said mountingmeans, said mounting member and receiving means being positioned withinsaid first device, and a securing member, said securing member lockingsaid receiving means within said first device.